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Do-it-yourself polishing of aluminum: methods, tools, devices

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Many people are aware that polishing aluminum gives us “pleasure”, but when dragging Alu-magic from behind a hill, I constantly want to rub something on them. This time, aluminum trims from my VOLVO caught my eye. DiyshaMetelkin said that I’m doing garbage, but still decided to help.

We started from 400 sandpaper to 4000, finished with Alu-magic. Appreciate ...

The result is that the metal on the bar is very soft, easily scratched, it’s not shorter for you! There is a specificity ... But you can polish any aluminum - teapots, cans, luggage racks, spoons, pans ...

Methods of polishing aluminum: chemical method

This technology is environmentally friendly, simple and fairly fast. It can be implemented with acid-resistant steel, which will form the basis of the polishing bath. If the scope of work is relatively small, you can use porcelain crucibles. Acid solution is poured into the container:

Products are immersed in a hot solution, the temperature of which should vary from 90 to 120 ° C, the final value will depend on the type of aluminum. Exposure to the composition of aluminum is necessary for 30 seconds or minutes, repeat the action should be about 6 times. At intervals, the parts are washed, and they must be shaken constantly.

Chemical polishing of aluminum will be better if you use a drum rotating at a certain speed. After completion of such manipulations, a contact copper film will remain on the surface. It should be removed by washing the product under running water with a low temperature. This must be done in a catcher. In the next step, the products are treated with 30 percent nitric acid.

Additional work recommendations

Aluminum polishing can be carried out using alkali solutions:

  • trisodium phosphate,
  • sodium nitrate,
  • caustic soda
  • sodium nitrate.

Their temperature should be higher compared to the acid method, the limit is 120-140 ° C. It is necessary to maintain products about 5-20 seconds. When such a technique is used, aluminum loss will be approximately 8 μm of the total layer thickness.

Using Electropolishing

Polishing of aluminum can be carried out in another way. At the same time, it is possible to obtain a sparkling and smooth surface, and the cleaning is characterized by high quality. Electrolytes for such work in most cases have sulfuric and phosphoric acid, the remaining components will depend on the material.

Electrolytes can achieve shine after completion of work. For the process, the temperature should be lower than in the above case, the temperature limit will be from 60 to 90 ° C.

Polishing must be done within 5 minutes, while the current density can be 10-50 A / dm². The polishing process involves the use of lead cathodes, but there are other alloys that involve the use of stainless steel. Polishing requires the use of duralumin suspensions, as well as electrolyte baths with polyethylene, lead or fluoroplastic treatment. It is necessary to prepare alkaline electrolytes, they will be cheaper.

The parameters of the process will be affected by the composition of the electrolyte, the temperature limit can vary from 40 to 95 ° C, as for exposure, it lasts from 3 to 6 minutes, while the current density at the anode is from 3-20 A / dm². When choosing cathodes, nickel-plated should be preferred.

Features of decorative etching

Polishing of aluminum can be carried out in a decorative way. This technique acts as a subspecies of electro polishing. Aluminum alloys are etched by anodes according to the regime in a phosphorus-chromium electrolyte. A crystalline pattern forms on the surface of the products, which looks like rosettes or frost. All parts are hung on the anode rod, and then you can start processing. Manipulations should be carried out at a voltage of 25-30 V. By the end, the voltage rises to 35-40 V, the anode current density will be equal to the limit of 8-12 A / dm², while the temperature will vary from 50 to 80 ° C.

After about 20 minutes, a pattern appears. If the voltage starts to rise arbitrarily, then we can consider the process complete. After the end of the manipulations, the products are washed, dried well, anodic oxidation is carried out above them. Aluminum is then painted with organic paint.

Mirror luster of aluminum can be obtained by another method of anode etching, which is called sparkling. For this product, before and after the process are subjected to heat treatment according to a special scheme. You can use anode etching "snowball", which allows you to create a matte-sparkling surface.

What is the best way to use at home

Polishing paste is one of the most commonly used home polishing agents for aluminum polishing. This is due to the fact that the chemical compounds are toxic, they are dangerous to human health. For polishing, you can apply:

  • sand paper
  • hard brushes
  • varnish
  • rags
  • alcohol type cleaning products.

When choosing sandpaper, it is important not to overdo it with grit, because otherwise you will have to remove scratches. To increase wear resistance and give shine, it is better to use varnish.

Features of electrochemical polishing

Electrochemical polishing of aluminum involves the implementation of work by the method of parallel chemical and electrical effects. According to the technology of this method, the part acts as an anode electrode, a positive current source is connected to it. The workpiece with the current supplied to it must be immersed in a tank that is filled with electrolyte. The role of the second electrode are copper cathodes.

Using a polisher

A polishing machine is a very convenient way to give aluminum an initial shine. To do this, you can use a polishing wheel for 1000, which is wetted with water. Use a sponge or cloth to apply water to the area to be treated. Next, a polishing machine for 1400 revolutions per minute is turned on. At a similar speed, the spray will fly about 1 meter around.

The surface of the aluminum will warm up, the liquid will evaporate. You should be prepared for the fact that the circle will become clogged with aluminum "porridge". Therefore, every minute the machine should be stopped to wash the abrasive wheel with a wet sponge under running water. To do this, some craftsmen use a regular spray bottle.

The "porridge" should also be removed from the part. Mirror shine will turn out if you additionally use also felt. This stage is one of the most important. It will depend on him 80% of the final result. Felt should protrude 10 mm behind the base, the circle should be moistened by spraying it with a spray. The part is wetted with a damp sponge. The polishing paste is used coarse, its application should be carried out on the part, and not on the circle.

Conclusion

Do-it-yourself polishing of aluminum can be carried out by various means, but one of the most effective is paste. It does not contain ammonia additives and is able to gently clean the part from roughness and scratches. With this composition, you can achieve the initial shine. The protective layer will eliminate the occurrence of oxidation over a long period.

Polishing methods for aluminum

It is necessary to polish aluminum due to the physical and ergonomic features of this type of metal. In the process of constant use, products are often prone to chips and scratches, the formation of glazing losses, oxidation and the disappearance of the initial shine. To restore the details to their former appearance, they just need to be polished.

At the industrial level, such polishing methods are widely known:

  • chemical and electrochemical
  • electrochemical polishing
  • decorative etching.

These polishing methods are not suitable for use at home, as they involve the use of chemicals hazardous to domestic use, as well as specialized machines for grinding metal surfaces.

Fix deep scratches and align the plane

Before polishing aluminum, it is very important to qualitatively prepare the surface of the part for further procedures.

If the aluminum part is painted, then before the polishing process, the paint or corrosion layer must be removed using various solvents and a brush with a hard metal bristle.

After the old paint coat has been removed, the part must be wiped with a soft cloth or foam roller.

The next step is grinding, designed to remove from the surface of the part all visible defects, scratches of various depths and the formation of corrosion. For this, small pieces of sandpaper of large and small abrasive are used sequentially one after another.

Grinding aluminum with fine-grained sandpaper allows you to smooth the surface of the product and bring it in perfect condition for further manipulations.

We remove roughness with a polishing machine

Grinding machine is an indispensable tool for processing the surface of aluminum before the appearance of the initial radiance. The polishing machine has a so-called abrasive wheel, the coating of which will depend on the nature of the work and the material being processed.

The grinding process itself using a grinding machine will occur as follows:

  1. The polishing wheel and the aluminum section to be treated are wetted with water. For processing capricious products, the disk must rotate at a speed of 1400 rpm. It is necessary to provide that at such a speed of rotation, the spray will fly 1–1.5 meters, therefore it is necessary to take care of appropriate protection of the face and clothing.
  2. The processed plane will begin to heat up as a result of friction, and the water will evaporate. As a result of this interaction, irregularities and roughness will be removed, forming blockages from aluminum particles and water on the basis of the abrasive wheel. Every few minutes you must turn off the machine and rinse the disc under running water. Aluminum particles should be removed not only from the tool, but also from the surface of the product.
  3. To achieve a mirror finish, it is recommended to use felt. A nozzle of this material is put on the grinding disk so that the edges protrude 1-1.5 cm beyond the circle. The felt and the surface of aluminum must be moistened with water, after which aluminum is polished.

At the final stage, a polish (paste) is also used, which is applied exclusively to the aluminum surface. The polish will give aluminum a shine and reflective properties of the mirror.

Chemical and electrochemical methods of polishing aluminum

Chemical polishing of aluminum has a wide circle of admirers, since this technique is not only quick and convenient, but also safe from an environmental point of view. To implement the process of chemical polishing, it is necessary to have a steel plate resistant to various acids. The plate is placed on the bottom of a special bath for polishing metals.

If you need to process a small aluminum part, then instead of a bath, you can use porcelain crucibles.

Next, the niche for polishing is filled with a solution of the following acids:

The solution is heated to 90-120 degrees Celsius, depending on the particular composition of the aluminum alloy. Aluminum is immersed in an acid solution for 30–45 seconds, after which the part must be washed with water and thoroughly remove excess moisture by shaking. The procedure is repeated 5-6 times.

The quality of chemical polishing will be as high as possible if you use a special rotating drum. Once polishing is completed, a contact copper film can be observed on the surface of aluminum. It must be removed by washing the part with cold running water using a trap. At the final stage, aluminum is treated with nitric acid 30%.

Electrochemical polishing of aluminum is carried out by simultaneously affecting the object of polishing with electricity and chemical reagents. In the process of such grinding, aluminum is an anode electrode to which a current source with a positive pole is connected. A special container is filled with electrolyte, after which the product, which conducts electricity, is immersed in it. Copper cathodes are used as the second electrode.

Electropolishing

The electro-polishing of aluminum parts is known for the high quality of restoring the surface of a metal product and bringing it to a mirror shine and impeccable smoothness. Sulfuric or phosphoric acids most often act as a conductor of electricity.

The electrolyte is placed in a special bath with an additional layer of lead or polyethylene and is heated to a temperature of 60–90 degrees Celsius. Lead cathodes are attached to the aluminum part. The current density corresponds to 10-50 A / dm². The part should be machined in an electrolyte solution for approximately 5 minutes.

Decorative etching

Another interesting polishing method is decorative etching. This method can be attributed to electropolishing.

An aluminum component is exposed to anodes in a solution of phosphoric and chromic acids. As a result, a chaotic crystalline pattern appears on the surface of the product, resembling frost on glass.

On a special anode beam, all parts that need restoration are put on. During polishing, they are exposed to a voltage that rises from 25 to 40 volts, and the temperature changes from 50 to 80 ° C.

The "pattern" will appear only after 15-20 minutes of exposure. When the voltage starts to jump involuntarily, the polishing process can be considered complete. Aluminum is thoroughly washed with cool running water, then it is dried and painted with a special organic paint.

What you need to polish aluminum at home

To carry out the process of grinding and cleaning aluminum products yourself, you need to purchase a special paste for polishing aluminum. It is relatively safe if you follow the recommendations for using a polishing compound.

For polishing, you may also need:

  • sandpaper medium or small abrasive,
  • bristles with metal bristles,
  • varnish
  • alcohol-containing liquid
  • rags.

Varnish is needed to finish the part. It will increase the durability and protection of aluminum from further damage.

Which polish to choose

Polish for aluminum copes well with various defects and corrosion on the surface of products. The polish has a pasty consistency, making it convenient to use at home. There are several indisputable advantages of pastes for polishing aluminum:

  1. The pastes do not contain ammonia, their composition is not as aggressive and dangerous as in acid solutions in industrial polishing of metals.
  2. Effectively affect scratches and other defects on the surface of aluminum, restoring the details to their original appearance and shine.
  3. After using a special paste, a protective layer forms on the surface of the parts, which prevents oxidation for a long period.

There are many different brands of polishes. You should choose based on the nature of the work performed, the types of parts and the price category of the paste itself.

The easiest way to polish aluminum with your own hands

To polish aluminum at home with a special paste is quite easy:

  1. Using a hard metal brush, it is necessary to rid the surface of the part of paint residues and dirt.
  2. Sanding medium abrasive is necessary to process the part, overwriting all major defects and bumps.
  3. The sandpaper of a small abrasive is polished until its surface becomes as smooth as possible. You can skip this step and immediately use a special polish.
  4. A small amount of paste should be applied to aluminum and using a rag (it is advisable to use fabrics with a natural composition: cotton or wool) in a circular motion to rub the part with paint. After achieving the desired effect, the paste remains are removed with a clean cloth.

If after treating the aluminum surface with a polish, defects visible to the eye remain, the procedure is repeated.

  1. If desired, the polished part can be varnished, which will increase the wear resistance of the part.

If you had experience polishing aluminum products in an industrial or home environment, you can share your experience in the comments.

Grinding large defects, leveling the plane.

At the first step, we must remove a large amount of metal, for this we need a productive angle grinder.

It is convenient to use to align the plane soft support plate art. 50099 (она отлично "держит" плоскость) и самые экономичные круги на липучке с оксидом алюминия от компании Deerfos Р120.

Теперь наша поверхность ровная и имеет одинаковую шероховатость.

Далее мы должны уменьшить риски на поверхности профиля, чтобы нам было легче дальше обрабатывать деталь.

For this we use the same tool and Velcro wheels Deerfos P220.

Reducing surface roughness in circles with Velcro P220.

Now we can move on to a more delicate surface treatment with an orbital sander.

Roughness reduction with OShM

The processing of flat surfaces using OShM has undeniable advantages over traditional grinding using angle grinder:

  • Compliance with surface geometry, without distortion of the plane.
  • Absolute uniformity of processing.
  • Easy handling control due to moderate aggressiveness.

Reducing surface roughness using Bosch OShM and P220 wheels.

Since this processing method is less aggressive, we will start with the same graininess at which we completed the previous stage - P220.

Then we will lower the surface roughness with the help of OSH and using Velcro circles Deerfos:

This alternation of steps will allow us to quickly and easily make the surface completely uniform and prepare it well for polishing.

You can use fewer steps, but then you will spend more time on each of them and it will be more difficult to control the quality of grinding.

The product after grinding with P800 circles.

Now our product is prepared for the last, most crucial stage.

In order to obtain the highest quality surface, we will carry out polishing in two stages: preliminary and finish.

Pre-polished aluminum.

This combination of felt and paste allows you to remove all the risks from preliminary grinding of the surface and prepare it for finish polishing.

Finishing polishing will be done with the same tool and the softest polishing flannel circlescollected on special adapter (or use a ready-made kit).

One of the best pastes for finishing polishing any metals - 3M Marine Polishing Paste 09019.

Finishing polishing aluminum with flannel circles (2500 rpm)

The combination of flannel circles with finishing paste removes the smallest defects from pre-polishing from the surface, makes it uniform and gives maximum gloss.

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